Usage:
turn [ axis [ angle [ frames ]]] [ models  model-spec ] [ coordinateSystem  N ] [ center  center ] [ precessionTilt  tilt ]

Turn rotates models by angle degrees (default 1.5) around a specified axis (default y) for a specified number of frames (default 1). Turn is the same as roll except for the default number of frames. See the video mini-example. See also: rock, align, select, cofr, set independent, movie-related commands

The angle can be positive or negative. The models to rotate can be specified by model number(s) or ranges separated by commas and preceded by #. If no models are specified, all active models will be rotated.

A coordinateSystem can be specified by reference model number N, optionally preceded by #. Otherwise, the laboratory frame of reference will be used. Any axis or center specification of the form x,y,z will be interpreted in the reference coordinate system, and when further motions are applied to an ongoing rotation, the center and axis will remain pinned relative to the reference model.

The axis can be:

• x - X-axis (if laboratory coordinate system, horizontal in the plane of the screen)
• y - Y-axis (if laboratory coordinate system, vertical in the plane of the screen)
• z - Z-axis (if laboratory coordinate system, perpendicular to the screen)
• x,y,z (three values separated by commas only) - an arbitrary vector
• axisID - the identifier of an axis defined with Axes/Planes/Centroids or the define command; object IDs are listed in the Axes/Planes/Centroids table
• an atom-spec of exactly two atoms (not necessarily bonded or in the same model) or one bond. If two atoms, the order of specification defines a handedness, and right-handed rotations are positive. If a bond, the handedness is not under user control. A bond can only be specified by selecting it and using the word selected, sel, or picked; any atoms also selected at the time will be ignored. If a center is not specified separately, it will lie on the atom-atom or bond axis. If a separate center is supplied, only the direction of the axis will be used. The first model in the axis atom-spec will be used for reference frame pinning unless a center atom-spec or a coordinateSystem is also given.

• x,y,z (three values separated by commas only) - an arbitrary point
• an atom-spec of any combination of atoms and surface pieces. The center of the bounding sphere of the specified items will be used. The first model in atom-spec will be used for reference frame pinning unless a coordinateSystem is also given.
• any of the following keywords, to specify a center of rotation method for computing the center:
  • view (center of view method)
  • models (center of models method)
  • front (front center method)
  This does not change the current center of rotation method, but allows using a different one for the purposes of executing the command.

The precessionTilt option specifies an additional rotation about a moving axis that is carried along by the main rotation. The moving axis is offset from the main axis by tilt degrees (toward the vertical if axis is along the line of sight). The two rotations cycle at the same rate but in opposite directions around their respective axes. See the Wobble motion movie in the Chimera Animation Gallery.

Keyword options can be used in any order and the keywords can be truncated. Example:

turn 1,1,0 180 center 0,2.5,2.5 coord 2 models #1